Apparatus and method for recording image on printing plate

Abstract

A printing apparatus with a plate-making mechanism with a data modification part for modifying width of an original image in a subscan direction by computation to obtain a modified image and a controller for recording an image with its length in a main scan direction modified by shifting a writing clock in image recording. This allows reduction in the amounts of computation as compared with a case where modification against extension of a paper in the main scan direction and subscan direction is performed only by computation and makes it easy to control modification as compared with a case where the modification in the main scan direction and subscan direction is performed only by shifting the writing clock and a moving clock for a writing head. Thus, it becomes possible to easily correct the influence of extension of paper in printing.

1. An image recording apparatus for recording an image by irradiating a printing plate with a light beam, comprising:
 a holding drum for holding a printing plate; 
 a light emission part for irradiating said printing plate with a light beam to perform writing; 
 a rotation mechanism for scanning an irradiation position of said light beam on said printing plate in a main scan direction by rotating said holding drum relatively to said light emission part; 
 a moving mechanism for scanning said irradiation position in a subscan direction by moving said light emission part relatively to said holding drum along a direction parallel to a rotation axis of said holding drum; 
 a storage part for storing data of an original image; 
 an operation part for generating data of a modified image obtained by substantially modifying width of said original image in said subscan direction in consideration of extension of a paper caused by dampening water in printing with said printing plate, said modified image indicating said original image distorted in said subscan direction without being distorted in said main scan direction; and 
 a control part for controlling emission of said light beam according to said data of said modified image while shifting writing timing in said main scan direction by changing a cycle of a writing clock. 
 
   
   
     2. The image recording apparatus according to  claim 1 , wherein
 said operation part modifies said width of said original image in said subscan direction by deleting or adding pixels. 
 
   
   
     3. The image recording apparatus according to  claim 2 , wherein
 said operation part divides a pixel group constituted of pixels aligned in said subscan direction into a plurality of modification unit pixel groups as many as pixels to be deleted or added and determines a position of one pixel to be deleted or added from/to each of said plurality of modification unit pixel groups on the basis of a random number. 
 
   
   
     4. The image recording apparatus according to  claim 3 , wherein
 the number of pixels in each of said plurality of modification unit pixel groups is half to twice a value obtained by dividing the number of pixels in said pixel group by the number of said pixels to be deleted or added. 
 
   
   
     5. The image recording apparatus according to  claim 2 , wherein
 said storage part stores processing instruction data indicating positions of pixels to be deleted or added in said original image and substantially indicating distortion of said original image in said modified image, and 
 said operation part generates data of said modified image on the basis of said processing instruction data. 
 
   
   
     6. The image recording apparatus according to  claim 5 , wherein said processing instruction data comprises:
 commands for inserting a blank to one end of said subscan direction in an image space where said modified image is generated; and 
 commands for deleting or adding pixels in aligning pixels of said original image from said one end to the other end following said blank. 
 
   
   
     7. The image recording apparatus according to  claim 6 , wherein
 said light emission part emits a plurality of light beams aligned in said subscan direction, and 
 data of said modified image generated with said commands for inserting a blank is data for performing writing while continuously moving irradiation positions of said plurality of light beams in said subscan direction. 
 
   
   
     8. The image recording apparatus according to  claim 1 , wherein
 recording of an image onto said printing plate is started on the basis of some data before said operation part generates the whole data of said modified image. 
 
   
   
     9. The image recording apparatus according to  claim 1 , wherein
 said operation part obtains data of said modified image and data of shifting of writing timing in said main scan direction by said control part, on the basis of a printing result of a test pattern. 
 
   
   
     10. The image recording apparatus according to  claim 9 , further comprising
 an image pickup part for performing an image pickup of a paper on which said test pattern is printed, to acquire said printing result. 
 
   
   
     11. The image recording apparatus according to  claim 1 , wherein said control part performs writing in consideration of extension of said paper in said main scan direction in said printing. 
   
   
     12. A printing apparatus, comprising:
 a holding drum for holding a printing plate; 
 a light emission part for irradiating said printing plate with a light beam to perform writing; 
 a rotation mechanism for scanning an irradiation position of said light beam on said printing plate in a main scan direction by rotating said holding drum relatively to said light emission part; 
 a moving mechanism for scanning said irradiation position in a subscan direction by moving said light emission part relatively to said holding drum along a direction parallel to a rotation axis of said holding drum; 
 a storage part for storing data of an original image; 
 an operation part for generating data of a modified image obtained by substantially modifying width of said original image in said subscan direction in consideration of extension of a paper caused by dampening water in printing with said printing plate, said modified image indicating said original image distorted in said subscan direction without being distorted in said main scan direction; 
 a control part for controlling emission of said light beam according to said data of said modified image while shifting writing timing in said main scan direction by changing a cycle of a writing clock; and 
 a printing mechanism for performing printing with said printing plate on which an image is recorded by said light emission part. 
 
   
   
     13. The printing apparatus according to  claim 12 , wherein printing is performed by using said printing plate held by said holding drum. 
   
   
     14. The printing apparatus according to  claim 12 , wherein said printing mechanism performs multicolor printing. 
   
   
     15. The printing apparatus according to  claim 12 , wherein
 said operation part modifies said width of said original image in said subscan direction by deleting or adding pixels. 
 
   
   
     16. The printing apparatus according to  claim 12 , wherein
 recording of an image onto said printing plate is started on the basis of some data before said operation part generates the whole data of said modified image. 
 
   
   
     17. The printing apparatus according to  claim 12 , wherein
 said operation part obtains data of said modified image and data of shifting of writing timing in said main scan direction by said control part, on the basis of a printing result of a test pattern. 
 
   
   
     18. The printing apparatus according to  claim 17 , further comprising
 an image pickup part for performing an image pickup of a paper on which said test pattern is printed, to acquire said printing result. 
 
   
   
     19. The image printing apparatus according to  claim 12 , wherein said control part performs writing in consideration of extension of said paper in said main scan direction in said printing. 
   
   
     20. An image recording method of recording an image onto a printing plate, comprising the steps of:
 a) preparing data of an original image; 
 b) generating data of a modified image obtained by substantially modifying width of said original image in a predetermined subscan direction in consideration of extension of a paper caused by dampening water in printing with a printing plate, said modified image indicating said original image distorted in said subscan direction without being distorted in a main scan direction orthogonal to said subscan direction; and 
 c) performing image recording by irradiating said printing plate held by a holding drum with a light beam, 
 wherein an irradiation position of said light beam on said printing plate is scanned in said main scan direction by rotating said holding drum relatively to a light emission part, said irradiation position is scanned in said subscan direction by moving said light emission part relatively to said holding drum along a direction parallel to a rotation axis of said holding drum, and said light beam is emitted from said light emission part on the basis of data of said modified image in synchronization with scanning in said main scan direction and said subscan direction while shifting writing timing for said light beam in said main scan direction by changing a cycle of a writing clock in said step c). 
 
   
   
     21. The image recording method according to  claim 20 , wherein
 said width of said original image in said subscan direction is modified by deleting or adding pixels in said step b). 
 
   
   
     22. The image recording method according to  claim 21 , wherein
 a pixel group constituted of pixels aligned in said subscan direction is divided into a plurality of modification unit pixel groups as many as pixels to be deleted or added and a position of one pixel to be deleted or added from/to each of said plurality of modification unit pixel groups is determined on the basis of a random number in said step b). 
 
   
   
     23. The image recording method according to  claim 22 , wherein
 the number of pixels in each of said plurality of modification unit pixel groups is half to twice a value obtained by dividing the number of pixels in said pixel group by the number of said pixels to be deleted or added. 
 
   
   
     24. The image recording method according to  claim 21 , wherein
 data of said modified image is generated on the basis of processing instruction data indicating positions of pixels to be deleted or added in said original image and substantially indicating distortion of said original image in said modified image in said step b). 
 
   
   
     25. The image recording method according to  claim 24 , wherein said processing instruction data comprises:
 commands for inserting a blank to one end of said subscan direction in an image space where said modified image is generated; and 
 commands for deleting or adding pixels in aligning pixels of said original image from said one end to the other end following said blank. 
 
   
   
     26. The image recording method according to  claim 25 , wherein
 a plurality of light beams aligned in said subscan direction are emitted to said printing plate in said step c), and 
 data of said modified image generated with said commands for inserting a blank is data for performing writing while continuously moving irradiation positions of said plurality of light beams in said subscan direction. 
 
   
   
     27. The image recording method according to  claim 20 , wherein
 recording of an image onto said printing plate is started on the basis of some data before said operation part generates the whole data of said modified image. 
 
   
   
     28. The image recording method according to  claim 20 , wherein
 data of said modified image and data of shifting of writing timing in said main scan direction are obtained on the basis of a printing result of a test pattern. 
 
   
   
     29. The image recording method according to  claim 28 , further comprising the step:
 acquiring said printing result by performing an image pickup of a paper on which said test pattern is printed. 
 
   
   
     30. The image recording method according to  claim 20 , wherein writing is performed in consideration of extension of said paper in said main scan direction in said printing in said step c). 
   
   
     31. An image modification method of modifying width of an image in a predetermined direction, comprising the steps of:
 dividing a pixel group constituted of pixels aligned in a predetermined direction into a plurality of modification unit pixel groups as many as pixels to be deleted or added, said pixel group being not divided at regular intervals; 
 determining a position of one pixel to be deleted or added from/to each of said plurality of modification unit pixel groups on the basis of a random number; and 
 modifying said pixel group by deleting or adding said one pixel from/to a position determined in each of said plurality of modification unit pixel groups, 
 wherein the number of pixels in each of said plurality of modification unit pixel groups is half to twice a value obtained by dividing the number of pixels in said pixel group by the number of pixels to be added or deleted. 
 
   
   
     32. An image recording apparatus for recording an image by irradiating a printing plate with a light beam, comprising:
 a holding drum for holding a printing plate; 
 a light emission part for irradiating said printing plate with a light beam to perform writing; 
 a rotation mechanism for scanning an irradiation position of said light beam on said printing plate in a main scan direction by rotating said holding drum relatively to said light emission part; 
 a moving mechanism for scanning said irradiation position in a subscan direction by moving said light emission part relatively to said holding drum along a direction parallel to a rotation axis of said holding drum; 
 a storage part for storing data of an original image; 
 an operation part for generating data of a modified image obtained by substantially modifying width of said original image in said subscan direction, said modified image indicating said original image distorted in said subscan direction without being distorted in said main scan direction; and 
 a control part for controlling emission of said light beam according to said data of said modified image while shifting writing timing in said main scan direction by changing a cycle of a writing clock wherein 
 said operation part modifies said width of said original image in said subscan direction by deleting or adding pixels where said operation part divides a pixel group constituted of pixels aligned in said subscan direction into a plurality of modification unit pixel groups as many as pixels to be deleted or added and determines a position of one pixel to be deleted or added from/to each of said plurality of modification unit pixel groups on the basis of a random number, and 
 the number of pixels in each of said plurality of modification unit pixel groups is half to twice a value obtained by dividing the number of pixels in said pixel group by the number of said pixels to be deleted or added. 
 
   
   
     33. A printing apparatus comprising:
 a holding drum for holding a printing plate; 
 a light emission part for irradiating said printing plate with a light beam to perform writing; 
 a rotation mechanism for scanning an irradiation position of said light beam on said printing plate in a main scan direction by rotating said holding drum relatively to said light emission part; 
 a moving mechanism for scanning said irradiation position in a subscan direction by moving said light emission part relatively to said holding drum along a direction parallel to a rotation axis of said holding drum; 
 a storage part for storing data of an original image; 
 an operation part for generating data of a modified image obtained by substantially modifying width of said original image in said subscan direction, said modified image indicating said original image distorted in said subscan direction without being distorted in said main scan direction; and 
 a control part for controlling emission of said light beam according to said data of said modified image while shifting writing timing in said main scan direction by changing a cycle of a writing clock; and 
 a printing mechanism for performing printing with said printing plate on which an image is recorded by said light emission part, wherein said operation part modifies said width of said original image in said subscan direction by deleting or adding pixels where said operation part divides a pixel group constituted of pixels aligned in said subscan direction into a plurality of modification unit pixel groups as many as pixels to be deleted or added and determines a position of one pixel to be deleted or added from/to each of said plurality of modification unit pixel groups on the basis of a random number, and 
 the number of pixels in each of said plurality of modification unit pixel groups is half to twice a value obtained by dividing the number of pixels in said pixel group by the number of said pixels to be deleted or added. 
 
   
   
     34. An image recording method of recording an image onto a printing plate, comprising the steps of:
 a) preparing data of an original image; 
 b) generating data of a modified image obtained by substantially modifying width of said original image in a predetermined subscan direction, said modified image indicating said original image distorted in said subscan direction without being distorted in a main scan direction orthogonal to said subscan direction; and 
 c) performing image recording by irradiating a printing plate held by a holding drum with a light beam, 
 wherein an irradiation position of said light beam on said printing plate is scanned in said main scan direction by rotating said holding drum relatively to a light emission part, said irradiation position is scanned in said subscan direction by moving said light emission part relatively to said holding drum along a direction parallel to a rotation axis of said holding drum, and said light beam is emitted from said light emission part on the basis of data of said modified image in synchronization with scanning in said main scan direction and said subscan direction while shifting writing timing for said light beam in said main scan direction by changing a cycle of a writing clock in said step c), 
 said width of said original image in said subscan direction is modified by deleting or adding pixels in said step b) where a pixel group constituted of pixels aligned in said subscan direction is divided into a plurality of modification unit pixel groups as many as pixels to be deleted or added and a position of one pixel to be deleted or added from/to each of said plurality of modification unit pixel groups is determined on the basis of a random number, and 
 the number of pixels in each of said plurality of modification unit pixel groups is half to twice a value obtained by dividing the number of pixels in said pixel group by the number of said pixels to be deleted or added.